This invention relates to a bicycle crank and a method for manufacturing said crank.
More precisely, this invention relates to a bicycle crank comprising:
an elongated core with a first and a second end,
a first and a second insert arranged on the ends of said core, and
a high-resistance fibre coating incorporated in a plastic material matrix.
U.S. Pat. No. 6,202,506 describes a bicycle crank of the type specified above, wherein the inserts are foamed into a rigid plastic material forming the core of the crank. Said U.S. Pat. No. 6,202,506 describes a procedure for manufacturing a crank comprising the following steps: introducing into a mould one layer of fabric soaked in synthetic resin providing a partially open fibre-reinforced plastic casing, inserting a pair of inserts in the partially open casing, foaming the inserts with high-resistance foam, sealing the fibre-reinforced plastic material casing with at least one layer of fibre fabric soaked in plastic material, and hardening the fibre-reinforced plastic material and said foam.
U.S. Pat. No. 4,811,626 describes a bicycle crank formed by three separate elements: a crank arm and two end-pieces. The crank arm consists of an element of composite material formed by overmoulding of a synthetic resin on a tubular core of reinforced fibres such as carbon fibres or aramid fibres. The two end-pieces have respective connecting elements which are forcibly engaged within the corresponding end of the tubular element which forms the crank arm. The crank described in this document is not provided with a high-resistance casing and the end-pieces and the crank arm may consequently come apart.